The present invention is directed to a heat exchanger for a gas furnace, and more particularly to the arrangement of a serpentine combustion gas passage.
In a gas furnace, a plurality of heat exchangers are spaced apart to allow airflow and heat exchanger in the interstices therebetween. Each heat exchanger is formed from stamped planar surfaces enclosing a serpentine combustion passage which contains the hot flue gases. Heat is transferred through the walls of the serpentine passage to heat air passing between the plurality of heat exchangers and among the interstices. The heated air is then transferred to a zone requiring heating.
The transfer of heat from the enclosed serpentine passage to the airflow around the heat exchangers is facilitated by maximizing the length and area of the serpentine passage. U.S. Pat. No. 4,739,746 to Tomlinson is an example of a serpentine passage which provides a relatively long passage in a confined space. However, the arrangement of the Tomlinson patent can be optimized to provide a longer passage in a smaller confined space, thereby providing greater efficiency in heat transfer. Additionally, the arrangement is such that a cold spot, leading to deterioration of the heat exchanger material, is formed at the end of the first leg of the Tomlinson heat exchanger.